This paper presents an analysis of light scattering by surface particles on the sensor window of a missile during ascent flight. The particulate contaminant distribution on the window is calculated by tallying the number of particles in a set of size ranges. The particulate contamination at the end of the mission is predicted by adding the contributions from the events of ground and flight operations. The surface particle redistribution caused by vibroacoustic-induced surface acceleration was found to contribute the most to particulate surface contamination. The analytical surface obscuration calculation with a set of particle counts was compared with the results of the image analyzer measurement. The analytical results, which were calculated with a given function of particle shape depending on size, were more conservative than the measurement. A scattering calculation using a verified BSDF model showed that the scattering was less than 0.001 at 20 deg off the direction of the incident light in the mid IR wavelength when the surfaces were at Level 300 initially.
Prediction of Particulate Contamination on an Aperture Window
